Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F226/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen
  • C08F226/06—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen by a heterocyclic ring containing nitrogen

Definitions

• This invention relates to a process which is useful for preparing high molecular weight copolymers from vinyl monomers such as vinylpyridine and styrene.
• the process uses emulsion polymerization techniques and provides advantages of simutaneously achieving rapid polymerization rates and high molecular weight.
• Both styrene and vinylpyridine are well-known vinyl monomers. Styrene has been used in a wide variety of applications, and the polymerization of styrene has been studied extensively in both industrial and academic laboratories. In comparison, the commercial significance of vinylpyridine has been limited, although a wide variety of potential applications has been claimed. Copolymers with butadiene and styrene used in tire cord adhesives probably represent the largest volume application.
• Xn number average degree of polymerization
• N number of particles
• kp the rate constant for propagation
• M the concentration of monomer in the particles
• Ri the rate of generation of radicals.
• the molecular weight desired is achieved by selection of appropriate reaction conditions. Generally, in a given system, the molecular weight is controlled by selecting an appropriate temperature of polymerization and initiator concentration. These variables affect the molecular weight primarily through their effects on Ri. Lower temperatures and lower initiator concentrations decrease Ri and increase Xn.
• references of interest to the present invention include the following:
• Japanese No. 13,007 (1967)--This patent discloses the emulsion copolymerization of vinylpyridines with styrene.
• the copolymerization is performed at pH >7.05 by addition of alkali. No polymer is formed in the absence of added alkali.
• An example discloses a copolymer containing 75% 2-vinylpyridine by weight.
• This report differs from the current invention in several important respects.
• the polymerization is carried out at an extremely low solids content ( ⁇ 5%). This is undesirable because it results in very poor utilization of reactor capacity.
• the proportion of surfactant in relation to the monomer charge (20%) is very high, and, therefore, when the polymer is isolated, a large amount of surfactant is present to contaminate the polymer.
• Sodium lauryl sulfate is hydrolytically unstable in hot alkaline conditions such as those required for removal of monomers from the emulsion by steam
• the present invention provides a process for the emulsion copolymerization of vinyl monomers, particularly vinylpyridine and styrene, to a high molecular weight at a rapid rate.
• high molecular weight it is meant that the copolymer has an I.V. greater than 1.0.
• rapid rate it is meant that the polymerization is greater than 90% complete after about 2 hours.
• pH control in particular represents an important process variable which has unexpectedly been found to affect molecular weight.
• a method of producing a high molecular weight copolymer from vinylpyridine and styrene monomers having greater than 50 mole % repeating units from vinylpyridine by emulsion polymerization which comprises
• the preferred monomers to use with the process according to this invention are 2-vinylpyridine and styrene.
• 3- and 4- vinylpyridine are also useful.
• substituted styrenes are also contemplated as useful monomers.
• Useful surfactants are alkali salts of unsaturated fatty acids having 12 to 24 carbon atoms and alkyl sulfates in which the alkyl group has 8 to 20 carbon atoms.
• Preferred surfactants include unsaturated fatty acid soaps.
• sodium oleate is preferred.
• Many common surfactants, including fatty acid soaps, are inoperable in our experience.
• sodium stearate and sodium palmitate give unstable emulsions.
• the preferred range for the surfactant concentration is from 2.5 to 5.0% relative to the weight of monomer. Too little surfactant will not provide a good emulsion, and excessive surfactant will result in excessive foaming and contamination of the polymer after isolation.
• Suitable initiators include water-soluble initiators typical of those used in emulsion polymerizations. Sodium persulfate in particular is preferred. The initiator concentration may range from 0.1 to 3.0% based on monomer weight, with the preferred range being 0.5 to 1.5%. Initiator concentrations that are too low will result in unacceptably slow reaction rates, while concentrations that are too high will produce polymer too low in molecular weight.
• the polymerization is conducted in an aqueous medium at solids levels from 5 to 50%, with the preferred range from 10 to 25%. If the solids level is too low, the process will become impractical; and if the solids level is too high, the emulsion is not sufficiently stable.
• the pH should be maintained between about 10 and about 14, with 11 to 13 being preferred. If the pH is lower than about 10, a low polymerization temperature is required in order to achieve a high I.V., and the rate of polymerization becomes slow and unpredictable. The unpredictable nature of the reaction under these conditions is believed to be due to increased sensitivity of the polymerization to small concentrations of unidentified impurities present in the monomer. Care must be taken not to have the pH so high that the emulsion breaks.
• the temperature of polymerization for this process is dependent on the values of other process variables, but should be between 45° and 90° C. Temperatures between 45° and 70° C. are preferred. Temperatures that are too low will result in slow polymerization rates and erratic results. Temperatures that are too high will produce low molecular weight polymers.
• the solution is heated to 60° C. before adding the monomer mix. Sodium persulfate (1.0 g) is then added. After 18 hours, the polymer emulsion is poured into a beaker. The pH of the emulsion is 11.5. The emulsion is broken by the addition of saturated NaCl solution. The polymer particles are coalesced to produce an easily filterable product by heating to 65° C. with gentle stirring. The polymer is then collected by filtration and washed. The I.V. of the polymer is 1.02.
• Example 2 Effect of pH--A series of polymerizations is performed as in Example 1, but using distilled 2-vinylpyridine.
• the charge includes 100 parts monomer mix, 1.25 parts Na 2 S 2 O 8 , 3.5 parts Na oleate, and 500 parts water.
• the reactions are carried out at 43° C.
• Example 3 nothing else is added.
• the conversion is 51% after two hours and 81% after five hours. After 24 hours, the conversion is essentially 100%, and the pH is 8.9.
• the I.V. of the polymer is 1.20.
• Example 4 HCl (0.7 parts) is added. After 24 hours, the pH is 6.3 and no polymer is found after evaporation of water and monomers.
• NaOH 0.4 parts
• the conversion is 96% after two hours and essentially 100% after four hours.
• the pH of the emulsion is 10.3 and the polymer has an I.V. of 1.8.
• Continuous Polymerization at High pH--A continuous emulsion polymerization is conducted in a series of three continuous stirred-tank reactors with average residence times of 3.5, 5.0, and 5.0 hours.
• the feed composition consists of 100 parts monomer mix (80 parts distilled 2-vinylpyridine and 20 parts styrene), 4.0 parts Na oleate, 1.25 parts NaOH, 1.25 parts Na 2 S 2 O 8 , and 500 parts water.
• the feed is added in three streams, including a monomer feed (100 parts), an initiator feed containing 1.25 parts Na 2 S 2 O 8 , (250 parts), and a surfactant feed prepared from 2.00 parts NaOH, 3.50 parts oleic acid, and 250 parts water (250 parts).
• the polymerization is conducted at 60° C. Conversion is high in all reactors, and the polymer has an I.V. of 1.21.
• the pH of the emulsion is 11.8.
• Example 2 Batch Polymerization of 65/35 Poly(2-vinylpyridine-co-styrene)--The procedure of Example 2 is followed, but using caustic-washed monomer mix containing 65 parts 2-vinylpyridine and 35 parts styrene.
• the reaction temperature is 60° C.
• the emulsion pH is 12.0
• the product has an I.V. of 1.12.
• the copolymers have greater than 50 mole % repeating units from vinylpyridine and the conversion is greater than 90%.
• inherent viscosity (I.V.) is used in this application, it will be understood to refer to viscosity determinations made at 25° C. using 0.50 gram of polymer per 100 ml of a solvent composed of N,N-dimethylformamide.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polymerisation Methods In General (AREA)

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Cited By (4)

Citations (2)

• 1985
  • 1985-07-26 US US06/759,196 patent/US4593082A/en not_active Expired - Fee Related
• 1986
  • 1986-07-14 WO PCT/US1986/001434 patent/WO1987000537A1/en active IP Right Grant
  • 1986-07-14 EP EP86904640A patent/EP0235177B1/de not_active Expired - Lifetime
  • 1986-07-14 DE DE8686904640T patent/DE3676188D1/de not_active Expired - Fee Related
  • 1986-07-14 JP JP61503844A patent/JPS63500458A/ja active Granted
  • 1986-07-15 CA CA000513862A patent/CA1253292A/en not_active Expired
  • 1986-07-21 TR TR402/86A patent/TR23372A/xx unknown

Patent Citations (2)

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